The present invention relates to transport mechanisms for magnetic tape, and more particularly to means for removing accumulated impurities from the surface of a rapidly moving length of tape.
In some state of the art apparatus using magnetic tape, the need for removing accumulated impurities from the coated or magnetic surface thereof has been recognized and means provided for removing the impurities. Such means commonly take the form of rigid elements which contact the passing tape and scrape foreign substances from the front or coated tape surface.
While such cleaning devices have generally been acceptable in the past, newer digital equipment of the high density type is much more sensitive to the presence of foreign matter on the tape surface. Foreign substances often cause an increased separation between the surface of the tape and the reading or writing heads, which separation causes the heads to "skip" an area of the tape. In previous digital tape systems, a certain degree of skip could be tolerated due to the relatively large area of the tape occupied by individual regions of flux signals, or "bits" and the greater separation that can be tolerated (e.g. 200 microinches as compared with 70 microinches for the high density apparatus). With the advent of high density recording, however, the individual magnetized regions of the tape are much smaller so that even small particles of foreign matter on the tape surface can give rise to substantial and unacceptable gaps between the tape and the reading or writing transducers.
While it has been recognized that one source of foreign matter has been the uncoated or back side of the tape which, of course, comes into contact with the oxide coated surface when the tape is wound on a reel, no cleaning mechanisms have been devised for incorporation into digital tape transport equipment. Moreover, existing cleaning devices are not adaptable for cleaning the uncoated back surfaces of present tape materials. Not only are the tape back surfaces more susceptible of scoring or scratching, but the amount of foreign material which is accumulated upon the back surfaces is such as to cause an unacceptably large buildup of matter in the prior art cleaning devices. This rapidly renders the cleaning operation ineffective and may ultimately cause large accumulations of foreign matter to be transferred back to the tape.
It is therefore an object of the present invention to provide a device for cleaning the uncoated surface of a transported tape element.
It is another object of the invention to provide an improved apparatus for removing foreign material from the surface of a passing tape element.
Still another object of the invention is to provide a device for cleaning the surface of a tape element, which does not scrape or abrade the tape surface.